Captured control knob

ABSTRACT

Apparatus for preventing the removal of control knobs from the control section of a machine. Each knob includes a body section and a radially expanded flange at the lower end of the body section. The knob engages a control shaft of a controllable machine component that passes upwardly through a first panel so that the flange is positioned adjacent to the panel. A second panel having an opening for rotatably containing the body section of the knob is passed over the knob and, when secured in place over the first panel, captures the flange between the panels.

FIELD OF THE INVENTION

[0001] This invention relates generally to a control knob assembly, and specifically to a tamper proof control knob.

BACKGROUND OF THE INVENTION

[0002] More specifically, this invention relates to a control knob assembly for use in a packaged terminal air conditioning (PTAC) unit of the type generally found in hotels and motels or other similar public lodging places wherein the unit services a specific space within a building to provide comfort air to the space. The unit is generally contained within a sleeve that passes through an outside wall of the building and includes an indoor section that communicates with an indoor comfort area and an outdoor section that communicates with the surrounding ambient. The two sections are separated by a wall with most of the system components such as the system compressor, the motor for driving heat exchanger fans, and the control valve being located in the outdoor section. The wall separating the two sections is covered with an insulating material which limits the flow of heat between sections and acts as a sound barrier that shields the comfort area from system generated noise.

[0003] The indoor section of the unit typically contains a control panel containing one or more control knobs for regulating, among other things, the temperature output of the unit. These control knobs, for the most part, can be easily removed from the unit by an occupant of the space being serviced by the unit and, as a consequence, must be replaced at rather frequent intervals. Loss of the control knobs is not only an inconvenience to the proprietor of the lodging, but also to subsequent occupants who find they have no control over the space temperature. In addition, replacement of the knob can result in a considerable expense to the owner of the lodging.

SUMMARY OF THE INVENTION

[0004] It is therefore an object of the present invention to improve the security of publicly accessible control knobs such as those found in air conditioning units employed in hotels, motels, inns and other similar places of lodging.

[0005] It is a further object of the present invention to prevent the loss of control knobs mounted on publicly accessible air conditioning units.

[0006] Still another object of the present invention is to provide a tamper-proof control knob that can be easily retrofitted to an existing machine.

[0007] Another object of the present invention is to reduce the operating costs associated with air conditioning units of the type generally found in public lodgings such as hotels and motels by preventing the unwanted loss of the unit control knobs.

[0008] Yet another object of the present invention is to provide a tamper proof control knob for an air conditioning unit that is relatively inexpensive to manufacture and easy to install.

[0009] These and other objects of the present invention are attained in a machine having an accessible control assembly containing one or more control knobs for regulating the operation of various components within the unit. Each knob contains a body section having a radially extended flange at the lower end of the body section. The knob is arranged to engage the shaft of the component being controlled by the knobs so that the flange is positioned adjacent to and in parallel alignment with the a first lower panel. A raised upper cover panel having an opening for rotatably receiving the body section of the knob is mounted over the lower panel and is secured in place to capture the knob flange between the two panels whereby the knob cannot be removed from the assembly without first unsecuring the cover panel from the lower panel.

BRIEF DESCRIPTION OF THE DRAWING

[0010] For a better understanding of these and objects and features of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, wherein:

[0011]FIG. 1 is a perspective view of an air conditioning unit embodying the teachings of the present invention;

[0012]FIG. 2 is an enlarged side view in partial section showing a portion of the machine frame containing the control panel assembly of the air conditioning unit;

[0013]FIG. 3 is a further enlarged partial perspective view of the lower panel of the control panel assembly with the upper panel removed; and

[0014]FIG. 4 is a partial front elevation of the face of the control panel assembly illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring initially to FIG. 1, there is illustrated an air conditioning unit generally referenced 10, embodying the teachings of the present invention. The unit in this embodiment of the invention is a packaged terminal air conditioner sometimes referred to as a PTAC unit of the type generally used in hotels and the like to provide comfort air to a specific living area. Although this invention will be described with specific reference to an air conditioning unit, it should be evident from the disclosure below that it has broader applications and can be employed in association with any type of unit having easily accessible control knobs to prevent the unwanted loss of the knobs.

[0016] The unit is housed within a rectangular shaped sleeve 12 that is contained within an outside wall of the comfort area serviced by the unit. The sleeve typically has standard height and width dimensions so that various units provided by different manufacturers can be slidably received therein. The front of the unit includes a removable cover 13 that is supported upon the frame of the unit and which closes against the sleeve as illustrated. The cover has an inlet opening 14 through which returning air from comfort area being serviced is drawn into the unit and an outlet opening 15 through which conditioned air is discharged back into the comfort area to provide either heating or cooling, depending on the selected mode of operation of the unit.

[0017] The front cover 13 of the unit contains a recessed well 17 that is closed by a hinged door 18 that complements the general contour of the cover when placed in a closed position. The door, as illustrated in FIG. 1 is shown in an open position. A pair of control knobs 20 and 21 are shown mounted inside the well by which an occupant of the comfort area can regulate the function of the unit. As further illustrated in FIG. 4, knob 20 is a temperature control knob for varying the temperature of the comfort air discharged from the unit. Knob 21 is a mode select knob by which the mode of operation of the unit can be selected to provide either heating or cooling to the comfort region. Although two control knobs are utilized in the present embodiment, more or less knobs may be employed without departing from the teachings of the present invention.

[0018] As noted above, this type of control knob has been easily removable from the unit and over the course of time the knobs become lost for whatever reason and must be replaced. The control knobs utilized in the present invention have a tamper proof feature that minimizes loss of the knobs.

[0019] Turning more specifically to FIGS. 2 and 3, each of the control knobs contained in the well includes a cylindrical body section 30 and a radially expanded flange 31 that encircles the bottom portion of the body section. In practice, the body section and the flange are integrally molded of a suitable plastic. Each knob has an axially disposed opening that passes upwardly through the bottom of the knob to a predetermined depth so that the knob can pass over the distal end of a control shaft 35 that is related to a controllable unit component. The knob is coupled to the shaft by any suitable connection so that the knob and the shaft turn together as the knob is rotated in a desired direction.

[0020] The temperature control knob 20, for example, is mated to the control shaft 35 of a thermostat 36 mounted within the unit which regulates the conditioned air temperature that is discharged from the unit. The distal end of the shaft is passed upwardly through a lower panel 38 that forms a section of the machine frame 42 immediately below the well 17 in the front cover. In assembly, the flange of the knob is brought down adjacent to and parallel with the lower panel. Rotation of the knob in one direction from a center or neutral position increases the output air temperature of the unit while rotating the knob in the opposite direction lowers the output air temperature of the unit.

[0021] The mode selector knob 21 is similarly mounted upon the control shaft of a mode select switch (not shown). Turning the knob in one direction conditions the unit to provide cooling to the comfort region, while turning the knob in the opposite direction conditions the unit to provide heating to the comfort region.

[0022] The bottom wall 43 of the well 17 provides a second upper panel that is located in a spaced apart relationship over the previously described lower panel. The upper panel contains a pair of openings 44 for rotatably containing the body sections of the knobs therein. The size of the openings, however, are insufficient to permit the flange portions of the knobs to pass therethrough. As a result, the flanges are captured between the two panels in assembly. In order to remove the knobs from the assembly, the front cover of the unit must be first removed from the unit.

[0023] As illustrated in FIG. 3, the flange of the temperature control knob is equipped with an extended arm 49. Repositionable stop pins 50 are mounted in a preselected hole 51 formed in the lower panel on either side of the arm. The stops are arranged to intercept the arm as the knob is rotated, thereby limiting the operational temperature range of the unit. In assembly, the stop pins are located in the space between the panels and are not accessible to the general public. Removal of the front cover, however, permits authorized personnel to relocate the pins within preselected holes thus limiting the output of the unit within a desired range of temperatures.

[0024] Although the present invention has been described with specific reference to use in an air conditioning unit, it should be obvious to one skilled in the art that this invention has wider applications. In a further embodiment of the invention, the upper and lower panels can be secured together in assembly by a plurality of spacer bolts or screws such as screws 60 shown in FIG. 4. The bolts can be provided within tamper-proof heads requiring special tools for turning the bolts and thus discouraging anyone from removing the panels.

[0025] While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims. 

We claim:
 1. Apparatus for preventing the loss of easily accessed control knobs of a machine that includes: a lower panel having the distal end of a control shaft of a controllable machine component that passes through said lower panel; a control knob mounted upon the distal end of said control shaft for facilitating rotation of said shaft; said control knob having a body section and a radially disposed flange mounted upon said body section at the bottom of said body section, said flange being located adjacent to and in parallel alignment with the lower panel; and a raised upper panel mounted over the cover panel having an opening for rotatably containing the body section of said knob therein, said opening being insufficient to permit the flange from passing therethrough wherein said flange is captured between said upper and lower panels.
 2. The apparatus of claim 1 that further includes means for supporting the upper panel in spaced apart relationship with said lower panel.
 3. The apparatus of claim 1 wherein said body section of said knob is cylindrical in form.
 4. The apparatus of claim 1 that further includes a stop means for limiting the range of rotation of said knob.
 5. The apparatus of claim 1 wherein said body section and said flange are integrally molded of plastic.
 6. Apparatus for preventing the loss of easily accessible control knobs from the control section of an air conditioning unit that includes a machine support frame containing a first panel; at least one control shaft associated with a controllable component of the air conditioning unit, the distal end of said shaft passing upwardly through the first panel; a control knob mounted upon the distal end of said at least one control shaft for rotation therewith, said control knob having a cylindrical body section and a radially expanded flange mounted upon the body section that is adjacent to and parallel with the first panel; a front cover mounted over the front of the unit containing a second panel that is located in parallel spaced apart relation with said first panel and having an opening therein for rotatably containing the body section of the knob and being of a size insufficient to permit said flange to pass therethrough such that the flange is captured between the first and second panels.
 7. The apparatus of claim 6 wherein said second panel is located within a well in said front cover, and further includes a hinged door for closing said well.
 8. The apparatus of claim 6 containing a first control knob for controlling the output temperature of the unit and a second control knob for controlling the mode of operation of the unit.
 9. The apparatus of claim 6 wherein the control knob and the expanded flange are integrally molded of plastic.
 10. A method of mounting a control knob upon the shaft of a controllable component to prevent removal of the knob that includes the steps of passing the distal end of the shaft of the component through an opening in a first panel, providing a control knob having a cylindrical body section and a radially disposed flange section which is located at the bottom of said body section, mounting the knob upon the distal end of said shaft so that said flange is adjacent to said first panel, mounting a second cover panel over said control panel that has an opening for rotatably containing the body section of said control knob, and which prevents the flange section of the knob from passing through said opening whereby the knob is captured between said panels.
 11. The method of claim 10 that includes the further step of integrally molding the body section and the flange from plastic.
 12. The method of claim 10 that includes the further step of limiting the range of movement of said control knob. 